Injection syringe and protective sheath



Sept. I R. E. RASMUSSEN 2,254,449

INJECTION SYRINGE AND PROTECTIVE SHEATH Filed Aug. 29, 1940 Fig.4.

INVENTOR. Tfzc/mrc/ E Z c25Ajd556/7 Patented Sept. 2, 1941 ETD STATES r tics INJECTION SYRINGE AND PROTECTIVE SHEATH 2 Claims.

This invention relates to medical appliances and has particular reference to an improved hypodermic injection syringe and a protective sheath for the same.

The principal object of the invention is to provide a hypodermic syringe which can be accurately adjusted and controlled to inject a minute, uniform quantity of vaccine or other specific.

Certain members of the medical profession now employ serums and vaccines of a highly concentrated nature. The effectiveness of these medicines, in large part, depends upon the degree of concentration. Such concentrated specifics must be given in accurate and uniform amounts, and in many instances the quantity required is of such minute proportions that it is impossible to measure it with a conventional syringe.

It is, therefore, an object of this invention to provide a syringe that will measure and dispense, at a single stroke of the piston, a minute but accurate quantity of the desired fiuid.

In devices such as this, it is very important that the plunger be free to be reciprocated in the cylinder so that air bubbles may be expelled from the device before it is used. It is, therefore, another object of the invention to provide a device that has an accurate metering element which is used in combination with the plunger of the syringe, without in any wise preventing the free reciprocation of the plunger if desired.

It is a further object of the invention to provide a syringe with a metering mechanism and a sheath to prevent the mechanism from getting out of adjustment when not in use.

The foregoing objects and other advantages of the invention will become more apparent as the description proceeds, reference being made from time to time to the accompanying drawing, forming part of this disclosure, in which drawing:

Fig. 1 is a side elevation of the sheath for housing and protecting my improved syringe.

Fig. 2 is a longitudinal section taken substantially entire line 22 of Fig. 1, and showing my improved syringe in position in the sheath.

Fig. 3 is a longitudinal section taken through the body of the syringe.

Fig. 4 is a view taken substantially on the line 4-41 of Fig. 2.

Fig. 5 is a view taken substantially on the line 55 of Fig. 2, and showing a syringe in dotted lines to illustrate the functioning of the sheath as a support.

Fig. 6 is a view taken substantially on the line 6-6 of Fig. 2.

Fig. 7 is a section taken substantially on the line 7-1 of Fig. 3.

' Referring now more particularly to the drawing, it will be seen that in the embodiment of the device herein disclosed (Fig. 3), my improved syringe consists of a cylinder 9, in which is fitted the plunger I0. The cylinder 9 has a reduced end I l adapted to accommodate the conventional hypodermic needle I2. The opposite end of the cylinder 9 is slightly tapered, as at I3, upon which taper is press-fitted the bushing I4. The bushing Mis externally threaded, as at I4, and is adapted to engage the threads of the knurled nut I6. These threads are particularly fine so that the axial movement of the nut is perceptible only upon each revolution. The bushing I 4 is counter-bored as at H. The inside of the counter-bore I1 is provided with agroove I8 into which is fitted a spring I9, the ends of which ride'against the sides of the plunger IE! and provide. sufficient friction on the plunger ID to prevent the plunger from being rotated and also prevent it from being displaced axially.

I The bushing It is calibrated as at 26 (Fig. 2) and the nut 16 is calibrated as at 2|, so that the bushing I 4 and the nut I6 act in the capacity of a micrometer. The cylinder 9 may be calibrated as at 22, as is the practice with ordinary hypodermic syringes. The plunger 10 is provided with an enlarged head 23, which is adapted to ride against the shoulder 24 of the nut I6 and serves as a stop for the movement of the plunger Ill into the cylinder 9. It will be seen, therefore, that by adjusting the nut I'G on the bushing M, the length of the stroke of the plunger ID in the cylinder 9 may be controlled. In other words, the farther out the nut I6 is adjusted, the shorter will be the stroke of the plunger Ill.

In Fig. 1, I show a side elevation of the protective sheath 25 for housing my improved syringe. This sheath 25 may be made of a transparent plastic, glass or other material. It is substantially cylindrical in shape; however, I prefer to flatten two of the sides as at 25c, so that the device will not roll when laid on a table. I also provide a peripheral groove 25 in which the needle end of the syringe may be temporarily supported as shown in Fig. 5. This allows the syringe to be held in proper usable position and prevents the needle from touching objects that might contaminate it.

The sheath 25 is counter-bored as at 28, which counter-bore is adapted to accommodate the bushing I4, so that the syringe nests snugly in the sheath and is held against displacement. A

larger counter-bore 29 is provided for the nut l6. This counter-bore is of suflicient size to provide a clearance for the adjustable nut 16 so that there is no danger of the adjustment of thenut being changed when the device is held in the sheath. The sheath 25 is threaded as at 30, and is adapted to accommodate a closure cap 3|, which is provided on the inside with a packing member 32, which serves to insulate the syringe against shock. The bore 21 and the counterbores 28 and 29 meet such shape and size that it is impossible to injure the needle 14 upon in-' serting the syringe in the sheath 25.

It is possible to calibrate my improved syringe in any manner best suited for the conditions under which it is to be used. In the embodiment disclosed, I have shown calibrations in the metric system. The following is an example of the manner in which this improved syringe operates: With a plunger having an outside diameter of .100 inch, two and one-half full turns or tenquarter turns of the nut f6, will allow the plunger to move forward one-sixteenth of an inch. This would inject approximately .01 cubic centimeter of fluid. One-quarter'of a turn'would inject approximately .001 cubic centimeter, and one-eighth of a turn would inject .0005 cubic centimeter, etc. Thus',it will be" seen that with this device it is possible to inject very'minute quantities of any desired fluid.

In order to use my improved syringe, it is first removed from the sheath 25 and the nut I6 is turned inwardly so that the plunger I may have the benefit of its full stroke. The needle isthen inserted in alcohol or any other sterilizing fluid, and is cleaned by reciprocating the plunger in and out the full'length of its stroke. Finally expelling all of such sterilizing fluid, the needle is then inserted into vaccine or other specific to be used, preferablythrough a rubber stopper, and the specific is drawn into the syringe. It 'is advisable to reciprocate the plunger several tiines in order to expel any air that might be drawndn with the fluid. The cylinder is then partly filled by withdrawing the plunger the requisite distance. When this has been accomplished the syringe is then ready for metering the specific dose, which is accomplished in the following manner. The nut I6 is turned outwardly from its closed position slightly more than is necessary for the required dose. The plunger is then pushed until the head 23 rests against the shoulder 24, thus expelling all of the fluid up to that point. The adjusting nut I6 is then rotated in the opposite direction a distance corresponding to the distance the plunger must be moved into the syringe in order to inject the amount of dose required. Successive injections may then be made by turning the nut inwardly to provide new stops for the movement of the plunger.

It will thus be seen that rapid and successive injections of the same or difierent quantities may be made accurately with this device. After the required injections are made, the syringe may be returned to the protective sheath until it is desired to use it again. Some of the fluid may remain in the syringe without the danger of having it expelled'inasmuch as the syringe is held within the sheath in such manner that it is impossible to distort or move the adjustment. If desired, a bit of cotton containing an antiseptic may be inserted in the bottom of the sheath to protect and sterilize the needle.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. The combination with a conventional syringe, of a micrometrical unit adapted to limit the stroke or the syringe plunger, said unit comprising a short calibrated bushing having a bore adapted to telescope one end of the syringe barrel, external threads near the free end of said bushing, and an internally threaded cap member adapted to cover the free end of said bushing, there being calibrations on the rim of said cap arranged to co-operate with the calibrations on said bushing.

2. The combination defined in claim 1, in which the calibrated bushing is provided with a portion which overhangs the end of the syringe ed to house a frictional plunger contact member.

RICHARD E. RASMUSSEN. 

